The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Hybrid powertrain architectures include torque-generative devices, including internal combustion engines and electric machines, which transmit torque through a transmission device to a vehicle driveline. Exemplary electro-mechanical transmissions are selectively operative in fixed gear modes and continuously variable modes through actuation of torque-transfer clutches. A fixed gear mode occurs when rotational speed of the transmission output member is a fixed ratio of rotational speed of the input member from the engine, typically due to actuation of one or more torque-transfer clutches. A continuously variable mode occurs when rotational speed of the transmission output member is variable based upon operating speeds of one or more electrical machines. The electrical machines can be connected to the output shaft via actuation of a clutch, or by direct connection. Clutch activation and deactivation is typically effected through a hydraulic circuit, including electrically-actuated hydraulic flow management valves, pressure control solenoids, and pressure monitoring devices controlled by a control module.
It is known to utilize one-way clutches to ground a rotatable driving member or input member such as an input race or first coupling plate, to a transmission housing/casing. In application, the clutch is engaged when the driving member is rotating in a first direction. When the driving member is in an opposite or second direction, the clutch will release or decouple the driving member from being grounded. Once released, the driving member is free to rotate in the second opposite direction. In this mode, the one-way clutch is free to overrun or “freewheel.” The driving member can include a transmission input member coupled to the engine. When the driving member rotates in the first direction it is grounded due to engagement of the one-way clutch, and thus, back-torque applied to the engine is inhibited.
It is known to assume current slip diagnostics are directionally independent for hydraulically actuated clutches. Thus, an assumption is made that a hydraulically actuated clutch has equivalent capacity in either direction. However, one-way clutches, such as mechanical diodes, only have capacity in one direction and freewheel in the other opposite direction. Accordingly, it is not desirable to apply slip speed based clutch slip detection to mechanical diodes when a load is applied in the freewheeling direction.